Auckland Transport chose the path of least resistance for its first big test of Hop cards on trains yesterday - by leaving most new electronic gates open to avoid any passenger crush.

Barriers were kept across only three of 15 electronic gates at peak travel times at Britomart's main entrance to train platforms, as most passengers were ushered off platforms clutching paper tickets.

They were mainly sent in a relatively free flow through alternative manually operated gates while an estimated 15 per cent with new rail-enabled Hop cards were shown how to tag off through ticket readers on the open electronic gates.

At the only other gated station on Auckland's rail network, Newmarket, it was deemed quiet enough for all barriers to operate.

One young man was escorted to the ticket office to pay a fare after an alarm told Veolia staff he had tried to escape charge by tailgating another passenger through the gate.

Despite a small army of Auckland Transport ambassadors passing around word of the new system, the man pleaded ignorance to the Herald.

But Auckland Transport chief executive David Warburton said only a handful of the estimated 70 per cent of rail passengers starting or ending their trips at gated stations were caught not paying, and he believed the new system would help to stem revenue losses.

Although most of Veolia's "revenue protection" staff were concentrated at the two stations yesterday, risking losses among the other 30 per cent, Dr Warburton said more would be sent out to patrol other parts of the network once passengers became used to the system.

"The public have been most supportive - we need to be careful we don't gear the system on assuming that everybody is dishonest," he said.

Auckland Transport has sold about 16,000 rail-enabled Hop cards since early last week, making Dr Warburton confident all the electronic gates would be operating full-time within about 10 days.

AT Hop card

Trains - already in place.

Ferries - from November 30.

Buses - between April and June (when early version Hop cards will be phased out)